Filaments and Dense Cores in Taurus Probed using the 100m GBT
Youngmin SeoJet Propulsion Laboratory, California Institute of Technology
Collaborators: Paul F. Goldsmith, Yancy L. Shirley, Derek Ward-Thompson, Jason M. Kirk, David Frayer, Rachel Friesen, Jeong-Eun Lee, Sara Church,
Glen Langston, Joe Masters, Robert W. Garwood
© 2017. All rights reserved.
Star formation in Molecular Clouds
Formation of Filaments & Dense Cores
Gravitational Collapse of Dense CoresFormation of Star
Collapse of Molecular Cloud
• A complete view of star formation processes from a molecular cloud to protostars is required.
TaurusSerpensOrionIRDCsEtc.
L1544L183L694L63Bok GlobulesEtc.
1. Probing Filaments and Dense Cores using KFPAGBT KFPA (2012A, 2013A)Dense Structure Survey in NH3, CCS, HC7NObservation time: 90 hoursMedian rms: 0.1 KLowest rms: 0.058 K
GBT Argus (2016B, 2017B)Collapse & Fragmentation Survey in HCN & HCO+ for infall survey, and N2H+ & NH2D for fragmentation surveyObservation time: 10 hours out of 70 hoursMedian rms: 0.15 KLowest rms: 0.08 K
2. Probing Collapse & Fragmentation of Dense Cores
using Argus
Anatomy of L1495-B218 Filaments in Taurus
500 µm dust continuum
13CO 1-0
[Palmeirim et al. 2013]
[Goldsmith et al. 2008]
Filaments
Hub50% of protostarsare at the hub
Anatomy of L1495-B218 Filaments in Taurus
Converging or shear flow[Goldsmith et al. 2008, Narayanan et al. 2008]
Probing Filaments & Dense Cores KFPA: NH3, CCS, HC7N
500 um dust continuum
Gal
acti
c la
titu
de
500 µm dust continuum
GBT KFPA NH3 (1,1)Showing intermediate & high density gas
[Seo et al. 2015]
Regions with Class I/II
Hub50% of protostarsare at the hub
GBT KFPA NH3 (1,1)
GBT KFPA CCS 21 - 10Showing chemically young gas
Showing intermediate & high density gas
Probing Filaments & Dense Cores KFPA: NH3, CCS, HC7N
[Seo et al. 2015]
Regions with Class I/II
Dense Cores IdentificationIdentifying NH3 structures using a dendrogram algorithm
39 leaves & 16 branches
[Seo et al. 2015]
• Pressure-confined structure → gravitationally bound structure → Star formation
Only 9 out of 39 leaves are gravitationally bound
7 out of 9 gravitationally bound leaves are active
Physical Properties of Dense Cores
Pressure-confined
Gravitationally unstable
growth bylarge scale converging CO flow
• Pressure confined structures:
No gravitational fragmentation
Dense cores in evolved regions
12m AROInfall speed:0.8 km/s
Infall speed:0.1 km/s
L1495A-N1521D
[Seo et al. in prep]
GBT Argus, HCN 1-0 and HCO+ 1-0Infall: 0.9 km/s
[Seo et al. in prep]
Blue: HCN, Black: HCO+
• Highly asymmetric infall motion in L1495A-N from Argus mapping
• Unusually strong infall motion in L1495A-N
Probing Filaments & Dense Cores using Argus
Hub
- Peak infall motion: >Mach 4
- The collapse predicted by similarity solutions: Mach 3.3 [Larson 1969, Penston 1969]
- Similar to shock-induced collapse [Gong & Ostriker 2009]
- L1495A-N may form and collapseby colliding flow.
13CO 1-0
Probing Filaments & Dense Cores using Argus
- Collapse time expected to be significantly short (<0.5 Myr)
Infall: 0.09 km/s
Infall: 0.04 km/s
Infall: 0.05 km/s
[Seo et al. in prep]
• L1521D is slowly collapsing at half the sound speed.
Blue: HCN, Black: HCO+
Probing Filaments & Dense Cores using Argus
GBT Argus, HCN 1-0 and HCO+ 1-0
FilamentL1521D
Two Modes of Star Formation
Within filament(L1521D)At the hub(L1495A-N)Fast star formation by converging large-scale flowsStellar group/cluster formation
Slow star formation by quasi-static gravitational collapseIsolated star formation
Overall: Pressure-confined structure → gravitationally bound structure → Star formationIn detail: two modes, Fast and Slow[Seo et al. in prep]
Star Formation & Argus+Getting a complete view of star formation processes in molecular clouds
General star formation processes within a molecular cloud (Large maps)+
Individual star formation (High spatial and spectral resolution)
• Connecting dynamics of a molecular cloud and individual star formation
Footprint ofArgus+
• Comparison of star formation processes between molecular clouds(Argus+ Gould Belt survey, IRDC survey)
Star Formation & Argus+Getting a complete view of star formation processes in molecular clouds
Footprint ofArgus+
• Connecting dynamics of a molecular cloud and individual star formation
• Comparison of star formation processes between molecular clouds(Argus+ Gould Belt survey, IRDC survey)
• Serpens South (~440pc)
